1. Field of the Invention
The present invention relates to a speed change display control device for a traveling work vehicle that includes: a main speed change device switching between speed change stages without interrupting transmission of drive power; an auxiliary speed change device switches between speed change stages accompanied by an interruption in the transmission of drive power; and a speed change controller outputting a speed change control command to the main speed change device and the auxiliary speed change device and creating a vehicle speed change ratio with combinations of main speed change stages of the main speed change device and auxiliary speed change stages of the auxiliary speed change device.
2. Description of Related Art
In order to achieve various speeds (vehicle speeds) appropriate to work travel and road travel in a traveling work vehicle such as a tractor, a speed change controller is commonly used which combines a main speed change device and an auxiliary speed change device to create a vehicle speed change ratio of twenty or more speeds.
For example, Japanese Patent Laid-open Publication No. 2008-57674 discloses a work vehicle that includes a main speed change device having eight speed change stages and an auxiliary speed change device having three speed change stages. The speed change stage of the main speed change device is determined by a main speed change lever, which can be operated to speed change positions for speed 1 to speed 8. The speed change stage of the auxiliary speed change device is determined by an auxiliary speed change lever, which can be operated to three speed change positions. The operation positions of the main speed change lever are displayed on a display having seven segments. Therefore, a driver can set a desired speed change stage from among the eight speed change stages while looking at the display.
An agricultural tractor disclosed by Japanese Patent Laid-open Publication No. 2009-214877 includes a main speed change device, which achieves eight speed change stages through combination of a four-stage first main speed change device and a two-stage second main speed change device; and an auxiliary speed change device, which is capable of three speed change stages. Because a main clutch switching operation is required when operating the auxiliary speed change device, a main clutch pedal is depressed and an operation lever is operated in a front/back direction or a left/right direction, and the main clutch pedal is released after the speed change operation. In addition, with respect to the main speed change device, speed is changed by pressing down an acceleration switch and a deceleration switch provided to a knob on the operation lever. Specifically, by pressing an acceleration switch 37 in order from speed 1, the speed is changed one stage at a time, up to speed 8. When the main speed change device is instead in the speed 8 position, by pressing the deceleration switch in order, the speed can be reduced from speed 8 to speed 1. A display of the selected speed change stage is given via a liquid crystal display provided to an instrument panel. The speed change position of the auxiliary speed change device is displayed in a top left area of the liquid crystal display, and the speed change position of the main speed change device is displayed in reverse on a right side of the liquid crystal display.
In traveling work vehicles such as those described above, a plurality of speed change stages are obtained through the combination of a main speed change device and an auxiliary speed change device. However, employing the correct speed change stages in a simple manner in order to achieve smooth work travel has not yet been achieved. In view of this, the present invention provides a speed change display control device capable of correctly employing a plurality of speed change stages obtained by combining a main speed change device and an auxiliary speed change device.